I've found this essay on cinematographydb.com on the cinematography by Lubezki in Birdman.
Lubezki, who is famous for his work with Terrence Malick, here uses essentially two primes throughout the film: a 12mm and 16mm on the Alexa (which are 18mm and 24mm on full frame, very very wide). I was impressed with how natural is the look: Lubezki's style is never "highly stylized", despite of the extreme wide angles. The article is rich of BTS, really glad to share it :)
http://www.cinematographydb.com/2014/11/cinematography-birdman-emmanuel-lubezki-asc/

Great find. It makes sense that those wide lenses made the constant camera movement in those close confines of the theater much more doable and not at all motion sickness inducing. But it's amazing they were using the wides for closeups as well. Ha, no big nose actors need apply. I will have to re-watch this to see how they pulled this off. @AlbertZ Thanks for posting this.

Originally they wanted to do a film without editing cuts at all. It does have cuts eventually but the camerawork is still based on no-cuts concept. All dialogs, all wide to close-up perspective changes are shot by steadicam moves, there is no classic from-behind-the-shoulder opposing views. Hence the choice of wide-angle lenses which work best for steadicam job.

Definitely an interesting piece of out of the box thinking camerawork breaking many dogmas.